Optical module

ABSTRACT

The present invention relates to an optical module, and more specifically, to an optical module which allows an optical coupling loss of an optical signal to be minimized and a frequency bandwidth thereof to be maximized. The optical module according to an embodiment of the present invention includes: a circuit substrate; an electronic element mounted on one surface of the circuit substrate; an optical element mounted on another surface perpendicular to the one surface of the circuit substrate; a capacitor mounted between the electronic element and the optical element; and an optical waveguide array on which an optical waveguide is disposed.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2017-0091024, filed on Jul. 18, 2017, the disclosureof which is incorporated herein by reference in its entirety.

BACKGROUND 1. Field of the Invention

The present invention relates to an optical module, and morespecifically, to an optical module which allows an optical coupling lossof an optical signal to be minimized and a frequency bandwidth thereofto be maximized.

2. Discussion of Related Art

As data traffic increases in the field of optical communication, amethod of transmitting a large amount of data at a high speed isrequired. As one example, a 100 Gbit or more optical transceiver moduleis formed as a multi-channel parallel connection type opticaltransceiver module in which optical transceiver modules have atransmission rate of 25 Gbit per unit channel, or uses a method oftransmitting data through wavelength division multiplexing (WDM).

As related arts, “Parallel Optical Interconnection Module and Method forManufacturing Thereof” (hereinafter, Related Art 1) is disclosed inKorean Patent No. 10-0461157, “Optical Receiver Module using WavelengthDivision Multiplexing Type” (hereinafter, Related Art 2) is disclosed inUS Patent Publication No. 2014/0169389, “Optical Module and Method ofAssembling the Optical Module” (hereinafter, Related Art 3) is disclosedin U.S. Pat. No. 6,874,952, and “Optical Module” (hereinafter, RelatedArt 4) is disclosed in Korean Patent Laid-open No. 10-2016-0088455.

In Related Art 1, a parallel optical coupling module to which an opticalwaveguide having a reflective curved surface is applied is disclosed. Ina structure disclosed in Related Art 1, since all light rays incident onthe reflective curved surface through the optical waveguide are nottotally reflected thereby but some of the light rays are emitted to anoutside of the optical waveguide, there is a problem in that an opticalcoupling loss occurs. In addition, in a case in which a process erroroccurs when the structure according to Related Art 1 is formed, there isa problem in that an additional optical coupling loss occurs due to theprocess error.

In Related Art 2, an optical coupling method in which an optical deviceincluding a mirror having a 45° inclination angle and an array lens isused is disclosed. However, the invention disclosed in Related Art 2 hasa problem in that a large optical coupling loss occurs even when aslight misalignment occurs between the optical device and aphotodetector.

In Related Art 3, an optical module having a structure in which a spaceris attached to an optical fiber array and a substrate to opticallycouple the optical fiber array and the substrate, and transmission linesare disposed on two perpendicular surfaces is disclosed. The structuredisclosed in Related Art 3 has a disadvantage in that a reflection lossis large at a high frequency because the transmission lines areperpendicular to each other, and thus a frequency bandwidth decreases.In addition, the structure disclosed in Related Art 3 has a disadvantagein that it is difficult to form patterns of the transmission lines and ahigh manufacturing cost is required to form the perpendiculartransmission lines.

In Related Art 4, a structure in which an optical waveguide is opticallyaligned with an optical element, and a glass rod in which a transmissionline is formed between the optical element and an electronic element isapplied thereto is disclosed. However, the structure disclosed inRelated Art 4 has a problem in that a high cost laser apparatus isrequired for forming the transmission line and an additionalmanufacturing time is required to form the curved glass rod, a pattern,and the like.

SUMMARY OF THE INVENTION

The present invention is directed to an optical module which allows anoptical coupling loss to be minimized and optical coupling efficiency tobe improved.

In addition, the present invention is directed to an optical modulewhich allows a frequency bandwidth to be maximized by an impedancematching structure being formed when an optical element and anelectronic element are electrically connected.

According to an aspect of the present invention, there is provided anoptical module including: a circuit substrate; an electronic elementmounted on one surface of the circuit substrate; an optical elementmounted on another surface perpendicular to the one surface of thecircuit substrate; a capacitor mounted between the electronic elementand the optical element; and an optical waveguide array on which anoptical waveguide is disposed.

An inclined surface may be formed between the one surface and theanother surface, and the capacitor may be mounted on the inclinedsurface.

The capacitor may be connected in parallel to the electronic element andthe optical element.

The electronic element and the capacitor may be connected via a firstwire, and the capacitor and the optical element may be connected via asecond wire.

In a case in which the optical module is formed as a multi-channeloptical module, the numbers of electronic elements each identical to theelectronic element, optical elements each identical to the opticalelement, and capacitors each identical to the capacitor corresponding tothe number of channels may be mounted on the circuit substrate, and thenumber of optical waveguides each identical to the optical waveguidecorresponding to the number of channels may be provided on the opticalwaveguide array.

In a case in which the optical waveguide array is coupled to the circuitsubstrate, the optical waveguide and the optical element may be closelydisposed to face each other.

The circuit substrate may be formed of a metal material, and the circuitsubstrate formed of the metal material may be used as a common ground ofthe electronic element, the optical element, and the capacitor.

Metal pads may be formed on surfaces of the circuit substrate on whichthe electronic element, the optical element, and the capacitor aremounted, and grounds of the electronic element, the optical element, andthe capacitor may be connected to the corresponding metal pads.

A capacitance value of the capacitor may be set according to aninductance component based on a length of the wire to perform impedancematching.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent to those of ordinary skill in theart by describing exemplary embodiments thereof in detail with referenceto the accompanying drawings, in which:

FIG. 1 is a perspective view illustrating one example of a multi-channeloptical module according to an exemplary embodiment of the presentinvention;

FIG. 2 is a side view illustrating the optical module of FIG. 1; and

FIG. 3 is a view illustrating an equivalent circuit of a wire connectingan electronic element and an optical element.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

In the embodiments of the present invention disclosed in thespecification, specific structural and functional descriptions aredirected only to providing examples for describing the embodiments ofthe present invention, and the embodiments of the present invention maybe implemented in various forms. The present invention is not to beinterpreted as being limited to the embodiments described in thespecification.

While the present invention may be modified in various ways and havevarious alternative forms, specific embodiments thereof are shown in thedrawings and described below in detail as examples. There is no intentto limit the present invention to the particular forms disclosed. On thecontrary, the present invention is to cover all modifications,equivalents, and alternatives falling within the spirit and scope of thepresent invention.

It should be understood that, although the terms first, second, and thelike may be used herein in reference to elements of the presentinvention, such elements are not to be construed as limited by theterms. The terms are only used to distinguish one element from another.For example, a first element could be termed a second element, and asecond element could be termed a first element without departing fromthe scope of the present invention.

It should be understood that, when an element is referred to as being“connected” or “coupled” to another element, the element may be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements. Other words used to describe relationships betweenelements should be interpreted in a like fashion (i.e., “between” versus“directly between,” “adjacent” versus “directly adjacent,” and thelike).

The terminology used herein to describe the embodiments of the presentinvention is not intended to limit the scope of the present invention.The articles “a,” “an,” and “the” are singular in that they have asingle referent, however the use of the singular form in the presentdocument does not preclude the presence of more than one referent. Inother words, elements of the present invention referred to in thesingular may number one or more unless the context clearly indicatesotherwise. It should be further understood that the terms “comprise,”“comprising,” “include,” and/or “including,” when used herein, specifythe presence of stated features, numbers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, numbers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein are to be interpreted as is customary in the art towhich the present invention belongs. It should be further understoodthat terms in common usage should also be interpreted as is customary inthe relevant art and not in an idealized or overly formal sense unlessexpressly so defined herein.

Meanwhile, when a certain embodiment may be implemented differently, afunction or operation described in a specific block may be performed ina different order from an order described in a flowchart. For example,two consecutive blocks may be performed substantially at the same timeor performed in an order opposite the described order according to arelated function or operation.

Hereinafter, an optical module disclosed in the present invention willbe described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view illustrating one example of a multi-channeloptical module according to an exemplary embodiment of the presentinvention, and FIG. 2 is a side view illustrating the optical module ofFIG. 1.

Referring to FIGS. 1 and 2, a multi-channel optical module 100 accordingto the exemplary embodiment of the present invention may include acircuit substrate 110, electronic elements 120, optical elements 130,capacitors 140, and an optical waveguide array 150.

Here, the optical waveguide array 150 is coupled to the circuitsubstrate 110, and particularly, the optical waveguide array 150 iscoupled to one surface (for example, one side surface) of the circuitsubstrate 110, on which the optical elements 130 are mounted, to facethe optical elements 130.

In addition, the circuit substrate 110 may be provided with a guide suchthat the optical waveguide array 150 dose not depart from apredetermined location.

Meanwhile, the electronic elements 120, the optical elements 130, andthe capacitors 140 are mounted on the circuit substrate 110, and opticalwaveguides 151 are disposed on the optical waveguide array 150.

In addition, the electronic elements 120 and the optical elements 130are connected by first wires 161, the optical elements 130 and thecapacitors 140 are connected by second wires 162, and the electronicelements 120 are connected to the circuit substrate 110 by third wires163.

In a case in which the optical module 100 is formed as a multi-channeloptical module, as shown in the embodiment, the numbers of the pluralityof electronic elements 120, the plurality of optical elements 130, andthe plurality of capacitors 140 mounted on the circuit substrate 110corresponds to the number of channels to be formed. Similarly, theplurality of optical waveguides 151 are disposed on the opticalwaveguide array 150.

In the embodiment, it is assumed that the optical module 100 is formedto have four channels, and according to such an assumption, fourelectronic elements 120, four optical elements 130, and four capacitors140 are mounted on the circuit substrate 110, and four opticalwaveguides 151 are disposed on the optical waveguide array 150.

In addition, for example, the electronic elements 120 may includedriving circuits, preamplifiers, and the like, and the optical elements130 may include light sources, photodetectors, and the like.

Meanwhile, the circuit substrate 110 may be formed in various shapes,and it is preferable for the electronic elements 120, the opticalelements 130, and the capacitors 140 to be easily mounted on the circuitsubstrate 110.

As one example, the circuit substrate 110 may be formed in a rectangularcolumn shape, the electronic elements 120 may be mounted on one surface111 (for example, an upper surface) of the circuit substrate 110, theoptical elements 130 may be mounted on another surface 112 (for example,one side surface) perpendicular to the one surface 111, and thecapacitors 140 may be mounted between the electronic elements 120 andthe optical elements 130, as shown in the embodiment.

Here, a corner between the upper surface 111 of the circuit substrate110 on which the electronic elements 120 are mounted and the one sidesurface 112 of the circuit substrate 110 on which the optical elements130 are mounted may be formed as an inclined surface 113 through achamfering method and the like, and the capacitors 140 may be mounted onthe inclined surface 113.

According to the embodiment, the optical elements 130 are mounted on theone side surface 112 of the circuit substrate 110, and the opticalwaveguide array 150 is coupled to the one side surface 112 of thecircuit substrate 110.

As described above, in the case in which the optical waveguide array 150is coupled to the one side surface 112 of the circuit substrate 110, theoptical waveguides 151 and the optical elements 130 are closely disposedto face each other.

Since the optical waveguides 151 and the optical elements 130 areclosely disposed to face each other, optical coupling efficiency betweenthe optical waveguides 151 and the optical elements 130 may bemaximized.

In addition, according to the embodiment, the capacitors 140 locatedbetween the electronic elements 120 and the optical elements 130 areconnected to the electronic elements 120 and the optical elements 130 bythe wires 161 and 162 such that the capacitors 140 serve asstepping-stones for wire bonding between the electronic elements 120 andthe optical elements 130.

An effect obtained in the case in which the electronic elements 120 andthe optical elements 120 are connected via the capacitors 140 will bespecifically described below.

FIG. 3 is a view illustrating an equivalent circuit of a wire in thecase in which the electronic element 120 and the optical element 130 aredirectly connected by the wire.

As illustrated in FIG. 3, in a case in which a high speed signal istransmitted through the wire, the wire may be represented with aninductance L and a capacitance C connected in series, and since thecapacitance C of the wire is very small, the inductance L is a maincomponent of the wire.

When the electronic element and the optical element are electricallyconnected, impedance matching for transmitting a high frequency signalis very important.

A relation between an impedance Z₀, the capacitance C, and theinductance L may be described by the following Equation 1.

$\begin{matrix}{{Z_{0} \approx \sqrt{\frac{jwL}{jwC}}} = \sqrt{\frac{L}{C}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

Since the capacitance C of the wire is very small and difficult toadjust, the impedance Z₀ of the wire is greatly affected by theinductance L, and in consideration of a characteristic in which theinductance L is proportional to a length of the wire, impedance matchingis performed by adjusting the wire length.

However, since a wire conventionally used for an optical module andhaving a diameter of 25 μm has a high inductance, a length of the wireis limited within several hundreds of micrometers to implement 50 ohmimpedance matching for securing a bandwidth of about several GHz.

Since the wire length is limited within a predetermined length forimpedance matching, in a case in which the electronic element and theoptical element are perpendicularly disposed, lengths of wires should belonger than those in a case in which the two elements are disposed onthe same plane.

Accordingly, in the case in which the electronic element and the opticalelement are perpendicularly disposed, since the length should increase,the inductance increases, and thus there is a problem in that animpedance mismatch occurs.

As one example for solving the impedance mismatch problem occurringbecause of an inductance increase due to an increase in wire length, thepresent invention proposes a structure in which the capacitors 140 aredisposed in parallel between the electronic elements 120 and the opticalelements 130.

That is, according to Equation 1, since an impedance mismatch occursbecause an inductance of a wire increases due to an increase in wirelength, when capacitance is increased in proportion to the increase ininductance, the problem of the impedance mismatch may be solved.

As described above, as an increased inductance of the wire iscompensated by increasing a capacitance thereof, the impedance of thewire may be set to a target value.

Accordingly, the impedance matching may be performed by adjustingcapacitance values of the capacitors 140 located in parallel between theelectronic elements 120 and the optical elements 130.

Meanwhile, the circuit substrate 110 formed of a metal material may beused for commonly grounding a surface on which the elements 120, 130,and 140 are mounted. That is, the circuit substrate 110 formed of themetal material is used as a common ground for the elements 120, 130, and140.

Alternatively, a method in which metal pads are formed on the threesurfaces 111, 112, and 113 on which the elements 120, 130, and 140 aremounted via metal (ex, Au) sputtering or gold (Au) plating and groundsof the electronic elements 120, optical elements 130, and the capacitors140 are connected to the metal pads via wire bonding may also be used.

According to the above-described embodiment of the present invention,since the optical waveguides 151 and the optical elements 130 areclosely disposed to face each other, optical signals may be input andoutput in a state in which an optical coupling loss due to changes inoptical paths between the optical waveguides 151 and active areas (forexample, light sources or photodetectors) of the optical elements 130 isminimized.

In addition, in the structure in which the electronic element 120 andthe optical element 130 are perpendicularly disposed, since each of thecapacitors 140 is applied between the electronic element 120 and theoptical element 130, an impedance due to an increase in wire length iscompensated, and thus an impedance matching structure adequate fortransmitting a high frequency signal may be implemented.

An operation of the optical module will be divided into opticaltransmission and optical reception and described below with reference toFIGS. 1 and 2.

In the optical reception, the optical module 100 is operated such thatan optical signal output from the optical waveguide 151 is incident on aphotodetector in the optical element 130 and converted into a currentsignal, and the converted current signal is input to the electronicelement 120 (for example, a preamplifier) via the capacitor 140.

In the optical transmission, the optical module 100 is operated suchthat an electrical signal is converted into a current signal by theelectronic element 120 (for example, a laser diode driving circuit), theconverted current signal is input to a light source in the opticalelement 130 (for example, a laser diode) via the capacitor 140, thelight source outputs an optical signal corresponding to the currentsignal, and the output optical signal is incident on the opticalwaveguide 151.

As described above, since an optical waveguide and an optical elementare closely disposed to face each other, an optical signal can be inputand output in a state in which an optical coupling loss due to a changein optical path is minimized.

Since a capacitor is applied between an electronic element and anoptical element, an impedance of a wire due to an increase in wirelength is compensated, and thus an impedance matching structure adequatefor transmitting a high frequency signal can be implemented. Therefore,a loss can be minimized and a frequency bandwidth can be maximized whenthe high frequency signal is transmitted.

In addition, embodiments of the present invention have advantages inthat a manufacturing process thereof is simplified and a cost forcomponents is decreased in comparison to a related technology.

While the optical module according to the present invention has beendescribed above with reference to the embodiments, the scope of thepresent invention is not limited to the specific embodiments, and thepresent invention may be implemented within a range clear to thoseskilled in the art by being modified and substituted with analternative.

Therefore, the embodiments and the accompanying drawings of the presentinvention should be considered in a descriptive sense only and not forpurposes of limitation. The scope of the present invention is notlimited by the embodiments and the accompanying drawings. It should beunderstood that the scope of the present invention is interpreted by theappended claims and encompasses all equivalent technological scopes.

What is claimed is:
 1. An optical module comprising: a circuitsubstrate; an electronic element mounted on one surface of the circuitsubstrate; an optical element mounted on another surface perpendicularto the one surface of the circuit substrate; a capacitor mounted on aninclined surface of the circuit substrate, the capacitor is mountedbetween the electronic element and the optical element; and an opticalwaveguide array on which an optical waveguide is disposed, wherein theoptical waveguide is disposed to face the optical element.
 2. Theoptical module of claim 1, wherein: an inclined surface is formedbetween the one surface and the another surface; and the capacitor ismounted on the inclined surface.
 3. The optical module of claim 1,wherein the capacitor is connected in parallel to the electronic elementand the optical element.
 4. The optical module of claim 3, wherein: theelectronic element and the capacitor are connected via a first wire; andthe capacitor and the optical element are connected via a second wire.5. The optical module of claim 1, wherein, the optical module is formedas a multi-channel optical module; a number of electronic elements, anumber of optical elements, and a number of capacitors corresponding tothe number of channels are mounted on the circuit substrate; and anumber of optical waveguides corresponding to the number of the channelsare provided on the optical waveguide array.
 6. The optical module ofclaim 1, wherein, the optical waveguide array is coupled to the circuitsubstrate, the optical waveguide and the optical element are closelydisposed to face each other.
 7. The optical module of claim 1, wherein:the circuit substrate is formed of a metal material; and the circuitsubstrate formed of the metal material is used as a common ground of theelectronic element, the optical element, and the capacitor.
 8. Theoptical module of claim 1, wherein: metal pads are formed on surfaces ofthe circuit substrate on which the electronic element, the opticalelement, and the capacitor are mounted; and grounds of the electronicelement, the optical element, and the capacitor are connected to thecorresponding metal pads.
 9. The optical module of claim 1, wherein acapacitance value of the capacitor is set according to an inductancecomponent based on a length of the wire to perform impedance matching.10. The optical module of claim 1, wherein capacitance is increased inproportion to an increase in inductance.
 11. The optical module of claim5, wherein the electronic elements, the optical elements, thecapacitors, and the optical waveguides are each identical to theirrespective electronic element, optical element, capacitor, and opticalwaveguide of a single channel optical module.